1. Field of the Invention
This invention relates in general to a guide for an optical fiber signal transmission cable and, more particularly, to an optical cable routing guide to direct the optical cable direction while minimizing signal transmission degradation and strain on the optical fiber.
2. Description of Related Art
Optical fibers are becoming more commonly used for signal transmission in communications and information handling applications. Optical fibers provide a large increase in the signal transmission bandwidth of a transmission cable compared to the bandwidth provided by conventional wire transmission cables. The increased bandwidth of optical transmission cables allows a greatly increased amount of signal data to be transmitted over comparably sized cables. In information handling applications, such as computer systems having large information storage capabilities, optical fiber transmission cables are used to provide connections between units of the computer system in order to most efficiently transmit large amounts of information from unit to unit. One example would be an ESCON interface between the computer systems.
While optical fiber cables provide a bandwidth advantage over the use of wire cables, the optical fibers have the disadvantage of being more fragile than metallic wires. Care in handling and in routing optical fiber cables is imperative to avoid damage to the optical fibers which can result in degradation of signal transmission. Sharp bends of the optical fibers in routing optical fiber cables must be avoided. Excessively sharp (small radius) bends can introduce microcracks in the optical fiber which degrades the transmission of optical signals. Also, because of the laws of optics governing light transmission, a small radius bend of the optical fiber can result in signal loss due to some of the transmitted light leaking out of the fiber at the bend.
The prior art recognizes the need to control routing of optical fibers and optical fiber cables by providing troughs for supporting optical fiber cables including curved troughs having a minimum radius of curvature to prevent bending of the optical cable too sharply. In addition, assemblies to provide strain relief of the optical fiber at optical fiber cable connectors connecting the cables to system units are known to the art. U.S. Pat. No. 5,530,787 to Arnett discloses an optical fiber guide for preventing sharp bends having a sleeve mounting member for mounting to a optical fiber connector. STK drawing 4112197 shows a similar approach. There are problems encountered with these approaches however. Specifically, the prior art ESCON connector brace strain relief depended upon the structure around the connector to prevent twisting, and additionally, it would only bend the strain relief in one direction.
For applications where system units are mounted on drawers or racks in enclosures such as cabinets, there is a need to protect the optical fiber cables from sharp bends at the connectors to the system units when drawers are moved and cabinet doors are closed. Since compactness of system unit mounting in an enclosure is a desirable feature, the protective guides for the optical cables should be as compact as possible and should be adaptable for directing the optical fiber cables in different directions.
Therefore there is a need for an optical fiber cable guide that is compact, easily installed and is adaptable to cable direction while providing the necessary protection from sharp bends.
It is an object of the present invention to disclose an optical fiber cable routing guide for protecting an optical fiber cable from sharp bends at or near to a cable connector that is totally independent of the surrounding structure in providing strain relief.
It is another object of the present invention to disclose an optical fiber cable routing guide that is attachable to the cable by pressing onto a connector strain relief boot connected to a optical fiber cable connector.
It is a further object of the present invention to disclose an optical fiber cable routing guide that may be attached to direct an optical fiber cable in either of two directions.
It is yet another object of the present invention to disclose an optical fiber cable routing guide that is easily installed without the need for tools and provides compact installation of optical fiber cables within an enclosure.
In accordance with the principles of the present invention, there is disclosed an optical fiber cable routing guide comprising an elongated curved channel having a generally U-shaped cross-section formed by an inner curved wall, an outer curved wall and a base. The curved channel supports and guides the direction of an optical fiber cable enclosed in a strain relief boot fixed to an optical fiber cable connector. A proximal end of the elongated curved channel is shaped to make abutting contact with the optical fiber cable connector so that protruding stud elements of the inner curved wall, the outer curved wall and the base prevent rotation of the cable routing guide relative to the cable connector. A distal end of the elongated curved channel is shaped to receive a collar feature on the strain relief boot to constrain the position of the cable routing guide on the strain relief boot with the proximal end of the curved channel in abutting contact with the cable connector.
The elongated curved channel is formed to have a radius of curvature to bend the optical fiber cable through an angle, usually in the range of 90xc2x0, while protecting the optical fiber cable from sharp (small radius) bends that could cause optical fiber damage or degradation of signal transmission. By choosing the radius of curvature of the curved channel to be as small as possible consistent with the bending constraints on the optical fibers and by reducing the length of the curved channel, the space needed to bend the cable through 90xc2x0 is minimized.
The optical fiber cable routing guide is manually installed over the strain relief boot fixed to the optical fiber connector without the need for any tools or fixtures such as clamps, clips or other holding means. The strain relief boot, as is known to the art, is a hollow tube formed of resilient material having a first end fixed to the optical fiber cable connector and a second end extending away (usually in the range of 1-3 inches) from the connector. The optical fiber cable is inserted through the tube of the strain relief boot into the connector for connection of the optical fibers as is well-known to those skilled in the art. The optical fiber cable guide is installed by inserting the strain relief boot into the opening of the U-shaped cross-section of the elongated curved channel forming the cable guide and pushing the cable guide toward the cable connector to make abutting contact of the proximal end of the curved channel with the cable connector. A collar at the second end of the strain relief boot is fitted into the shaped distal end of the curved channel to prevent the cable guide from moving away from abutting contact with the cable connector. The optical fiber cable guide may be installed on the strain relief boot in either of two orientations providing the ability to bend the optical fiber cable in a first direction, or alternatively, by rotating the optical fiber cable guide by 180xc2x0 with respect to the cable connector, to bend the optical fiber cable in a second direction opposite to the first direction.
The above, as well as additional objects, features, and advantages of the present invention will become apparent in the following detailed written description.